1. Field of the Invention
This invention relates to circuit interrupters and, more specifically, to vacuum circuit interrupters, such as, for example, vacuum circuit interrupters having a grounding device.
2. Background Information
Circuit breakers and other such devices provide protection for electrical systems from electrical fault conditions such as current overloads, short circuits, and low level voltage conditions. Typically, circuit breakers include a spring-powered operating mechanism which opens electrical contacts to interrupt the current through the conductors in an electrical system in response to abnormal conditions. In particular, vacuum circuit interrupters include separable main contacts disposed within an insulated and hermetically sealed vacuum chamber within a housing. Generally, one of the contacts is fixed relative to both the housing and to an external electrical conductor which is interconnected with the circuit to be protected by the circuit interrupter. The other contact is moveable. In the case of a vacuum circuit interrupter, the moveable contact assembly usually comprises a copper stem of circular cross-section having the contact at one end enclosed within the vacuum chamber, and a driving mechanism at the other end which is external to the vacuum chamber.
Vacuum interrupters are, typically, used to interrupt medium voltage alternating current (AC) currents and, also, high voltage AC currents of several thousands of amperes or more. Typically, one vacuum interrupter is provided for each phase of a multi-phase circuit and the vacuum interrupters for the several phases are actuated simultaneously by a common operating mechanism, or separately or independently by separate operating mechanisms. It is known to provide a three-position switching and isolating apparatus, including gas-insulated switch-disconnectors and isolators, suitable for use in medium voltage switchgear. Contacts for closing, breaking, isolation and earthing, or grounding, are arranged inside a cylinder in sulfur hexafluoride (SF6) gas typically at a pressure of about 202 kPa absolute. The contacts can take three positions: closed, opened and grounded. It is further known to electrically connect such a three-position switching and isolating apparatus in series with a circuit breaker or fuse, which may also interrupt the current.
It is desirable to integrate the current interruption and the grounding functions of a vacuum interrupter into a single device or mechanism. That is, it is desirable to have an operating mechanism that performs the function of separating the contacts within the vacuum chamber as well as the function of electrically coupling the load side contact with a grounded terminal, thereby grounding the load side of the circuit. The typical procedure for performing these operations was to separate the contacts, decouple the line side contact from the line terminal, couple the line side contact with a grounded terminal, and close the contacts. The devices for decoupling the line side contact from the line terminal, coupling the line side contact with a grounded terminal, however, are typically complex.
There is, therefore, a need for a simple device structured to decouple the line side contact from the line terminal, and couple the line side contact with a grounded terminal.
There is a further need for a device structured to decouple the line side contact from the line terminal, and couple the line side contact with a grounded terminal having a reduced number of components.